Design rules for matrix signs

One of the aspects seldom addressed in literature are the design rules for matrix signs: how should a given symbol be designed as a matrix sign? When several symbols are combined on one sign it is possible that one or more lightpoints may have to deviate from their regular grid. In that case it is important to know the maximum allowable deviation. The just-noticeable deviations in the grid structure of matrix signs was experimentally determined in the laboratory.